GAMMA-AMINOBUTYRIC ACID-IMMUNOREACTIVE NEURONS IN THE AMYGDALA OF THERAT - SEX-DIFFERENCES AND EFFECT OF EARLY POSTNATAL CASTRATION

The distribution of GABA-immunoreactive neurons in the rat amygdala wa s determined by immunohistochemical methods. Sex differences in the nu mber of GABA-immunoreactive cell bodies were observed in the medial, c entral, cortical and basolateral amygdaloid nuclei. Females had more n umerous GABA-expressing neurons than males (P < 0.01). Castration of n eonatal males had controversial effects on this sex difference in the different parts of the amygdaloid complex. In the cortical and basolat eral amygdala castrated males showed a female pattern of GABA-expressi on. In the central amygdala no effect of castration on the number of G ABA-immunoreactive cells was found. In the medial amygdaloid nucleus n umbers of GABAergic neurons in castrated males differed both from inta ct males and females. The results of the present study suggest that th e expression of GABA in the neurons of the amygdala is under complicat ed gonadal hormone regulation. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.